A myocardial infarction (MI or AMI for acute myocardial infraction), commonly known as a heart attack, occurs when the blood supply to part of the heart is interrupted. This is most commonly due to occlusion (blockage) of a coronary artery following the rupture of a vulnerable atherosclerotic plaque. This occurs through years of an undetected or untreated combination of hypertension and abnormally high levels of lipids in a patient's blood. With time a patient builds up plaque deposits in the interior lining of their coronary arteries. This condition is commonly referred to as Coronary Artery Disease (CAD).
In some patients, these plaque deposits become severe enough that a restriction in coronary artery blood flow occurs and the patient becomes symptomatic. These restrictions can be clinically detected via various diagnostic and exercise tests. The patient begins to experience pain (angina) as well.
The typical treatment for this patient population is a Percutaneous Coronary Intervention (PCI), also known as Angioplasty. A balloon on the end of a catheter is inflated to remove the restricting plaque deposits, and then a stent is placed to stabilize the repaired region. In some cases, the restrictions are so extensive and severe that a Coronary Artery Bypass Graft (CABG) procedure is required. If detected and treated early enough, this patient group can avoid the deleterious effects resulting from a heart attack.
However, some patients are not as fortunate. These patients are asymptomatic. Their CAD remains undetected or untreated, and at a point in time, a region of the plaque becomes vulnerable and a surface layer of inflammation develops. The inflamed region can rupture, expelling plaque material (calcified deposits) into the coronary artery. Platelets in the blood stream recognize this foreign material and encapsulate it. A blood clot forms in close proximity or just downstream from the ruptured region. This leads to a devastating chain of events for the patient. The blockage in a coronary artery prevents the flow of blood that contains vital oxygen to the myocardial tissue supplied by that coronary artery. The patient begins to experience symptoms such as intense pain. Typical treatments are an immediate PCI procedure or an immediate transfusion of an anticoagulant or thrombolytic agent to break or dissolve the blood clot. Time is of the essence. If not treated immediately, the affected myocardium will not receive sufficient oxygen supply and that region of cardiac muscle will literally die. This is referred to as a Myocardial Infarction (MI), also known as a heart attack. If the patient survives, the MI can lead to further complications with time, including a susceptibility to tachyarrhythmias and a loss of heart function through the mechanisms of heart failure. The worst outcome is not surviving the heart attack. This can happen when the coronary artery blockage is so severe that the patient experiences a lethal arrhythmia and can not be resuscitated.
The challenge is to detect, recognize, and successfully treat the patient before a blockage of a coronary artery occurs. This is what the American Heart Association (AHA) refers to as Acute Coronary Syndrome (ACS). This could be done in advance of the life threatening MI or the subsequent tachyarrhythmias. Preventing the MI and protecting patients from dangerous arrhythmias would be clinically important. It would save many lives through prevention of a first heart attack, and could have profound implications in cost savings to our health care system. Many of the subsequent complications resulting from heart failure could be avoided as well.